Field
The technology as disclosed herein relates generally to systems and methods for managing inbound aircraft and, more particularly, to systems and methods for safe approach and landing of aircraft of varied weight categories at multiple landing thresholds that are spaced a distance apart on a single runway at an airport.
Background
Air traffic continues to grow and capacity limitations at airports are resulting in flight delays. The capacity limitations, in part, are due to aircraft spacing requirements necessitated by wake turbulences created by leading, heavier aircraft that may be encountered by following, lighter aircraft, which limits how closely the following aircraft can be safely spaced behind leading aircraft during approach and landing. Specifically, aircraft that are approaching an airport to land are spaced by at least three to six nautical miles, depending on how light the following aircraft is in comparison to the leading aircraft, to allow the wake turbulence to dissipate.
Wake turbulence can be generated in the form of trailing vortexes from aircraft wings. The pair of vortexes created by each aircraft is a result of lift being generated by the wings and air rotating around the wing tip from the high pressure regions at the bottom of the wing to the lower pressure regions on the top of the wing. The strength of the vortexes is dependent on the instantaneous lift being generated by the wing and on the aircraft speed and configuration (stronger vortexes are generated at low aircraft speed). While there are ways to reduce the strength of the vortexes, they cannot be eliminated. The vortexes can severely buffet another aircraft that flies into them, and the vortexes from a heavy widebody transport aircraft can upend and destabilize a lighter weight narrow body transport aircraft following the heavier aircraft.
Present aircraft approach and landing spacing on a runway is established with the assumption of worst case conditions for wake vortex persistence in or near the flight path of a following aircraft. A set of Instrument Flight Rules (IFR) govern the management of commercial and many business aviation aircraft in most situations. In particular, for aircraft approaching a major airport, Air Traffic Control for the airport terminal area direct the aircraft pilots onto specific paths and specify speeds to merge the aircraft onto a single path for approach to a runway. This is done using rules for spacing the aircraft according to the weight categories of the leading and following aircraft.
In the United States, the Federal Aviation Administration (“FAA”) labels aircraft weight categories as Small, Large, Heavy, and Super. Internationally, as defined by the International Civil Aviation Organization (ICAO), the aircraft weights are categorized as Light, Medium, Heavy, and Super. By way of illustration when describing the technology as disclosed herein, the term “heavier” will refer to aircraft in the Heavy and Super categories—namely, all the wide-bodies; and the term “lighter” will refer to aircraft that are in the small, light, medium or large categories, namely, narrow-body, regional, and business aircraft.
The normal minimum longitudinal spacing between aircraft of similar weight, or between any leading lighter aircraft and a heavier one following, is three (3) nautical miles in an airport terminal area during the initial phases of the approach to the runway. This minimum longitudinal spacing is usually set by “radar separation” rules. When a heavier aircraft is followed by a lighter aircraft a larger longitudinal spacing is required behind the heavier aircraft, as directed by “wake separation rules, which may be, for example up to six (6) nautical miles. This reduces the amount of aircraft that can land over a period of time (“the landing rate”) on a single runway from the landing rate that can be achieved with approaching and landing aircraft of similar weights.
Aircraft follow a straight path on final approach to the runway, guided by a landing guidance system, for example, an Instrument Landing System (ILS). The ILS is a ground-based precision landing guidance system that provides lateral and vertical guidance to an aircraft following a landing flight path to land on a runway. The system uses radio signals to transmit guidance signals that along with high-intensity lighting arrays enable a safe landing, even when the visibility is poor. The actual names of the two components of the guidance signal from a landing guidance system are “glide slope” for the vertical component and “localizer” for the lateral component. The glide slope is the constant-angle, straight-line descent path that the aircraft is to follow to the landing zone on the runway just past the runway threshold. The angle of the glide slope is usually set at 3 degrees by the FAA. The ILS provides directional radio signals from the end of the runway that display on the aircraft cockpit instruments the proper direction and glide slope for the pilot to follow on descent to the runway landing threshold. The landing threshold is the line across the runway marking the nearest point to the physical end of the runway at which the aircraft is allowed to touch down on the runway. Most aircraft have an autopilot that can automatically follow the path specified by the ILS, should the pilot choose not to fly the approach manually.
Dual threshold approaches and landings have been proposed in which Air Traffic Control receives information about the arriving aircraft that includes the type and/or the weight category of each aircraft. Air Traffic Controllers are able to assign heavier aircraft to fly on a lower final approach flight path and lighter aircraft to fly on an upper final approach flight path by verbal instructions over a radio to the pilots. The aircraft then acquire the guidance from the landing guidance system for the assigned flight path and use the guidance to follow the assigned path, lower or upper, to the respective landing threshold. However, monitoring vertical separation is a challenge for Air Traffic Controllers making it impractical for Air Traffic Controllers to conduct dual thresholds final approaches and landing safely and economically. In addition, safely landing multiple aircraft of different weight categories on a single runway requires a system that provides notification to following aircraft of a deviation of a leading aircraft above its assigned vertical flight path during approach and landing. In addition, for each of the dual flight paths on final approach, a separate arrival route (lateral path over the ground), is required for aircraft of different weight categories to avoid wake encounters. Additional arrival routes are difficult to incorporate into the airspace around an airport.
Improved aircraft approaches to landing at airports, addressing the continued increase in air traffic and the runway capacity limitations at airports, are needed to prevent flight delays and increased costs.